Yahoo said that no financial information was included in the breach, but username, email addresses, telephone numbers, passwords, birth dates and, in some cases, answers to security questions were all part of the break in.

Why email hacks are so desirable

Your email account is the digital key to your kingdom for a variety of reasons, which is why they are so valuable to hackers.

Remember, whenever you (or a hacker) need to reset a forgotten password for just about any online account, the reset instructions get sent to your registered email account.

Another treasure trove is the accumulation of messages that you were sent when you initially signed up for any account, which is a quick way to know what other accounts can be compromised.

Lesson No. 1: Start getting in the habit of deleting sign-up, notification and reset email messages as soon as you are through with them.

Birthdays and security questions

Many sites ask for your birthday as a way to ensure you are old enough to meet their age requirements, but nothing says you have to give them your actual birthday.

Although Yahoo is moving away from security questions as a way to allow you to regain access to an account, the information gathered by the hackers can potentially be used elsewhere.

Questions such as “What was your high-school mascot?” are pretty easy to figure out depending on your profile on sites like Facebook and LinkedIn.